Data communication over unsecured communication links such as telephone lines is subject to detection and modification with a possible end result being the loss of a preferred position. In order to minimize or to totally eliminate the possibility of a compromise of the transmitted data message, various forms of encoding the message have been devised. The following is a list of those encrypter related patents known to applicants at the time of filing the present application:
U.S. Pat. Nos.
3,522,374, 3,614,316, 3,657,699, 3,731,197, 3,773,977, 3,781,473, 3,784,743, 3,798,359, 3,798,360, 3,808,365, 3,824,467, 3,911,216, 4,074,066, 4,078,152 and 4,004,089.
The following publications are deemed to be of interest for their showing of the state of the art, at the time of filing the present Application: "The Outlook For Computer Security" by Whitfield Diffie published in Mini-Microsystems, pages 42-44, October 1978, and "Putting Data Encryption To Work" by Carl H. Meyer and Walter L. Tuchman, published in Mini-Microsystems, pages 46-52. Each of the inventors of above cited patents and the authors of the aforementioned publications have appreciated the problem that occurs with the transmission of unencrypted data, namely, unauthorized access to the communicated data; and has attempted to solve the problem by encoding the to-be-transmitted data. Once the data is encoded, it is still not necessarily secure from unauthorized access. If the code used in the encoding process is relatively simplistic, it is just a matter of trial and error before the code is broken and unauthorized access is gained. In order to be secure from decoding attempts, which attempts now take advantage of the high power available in large-scale computers, it is necessary to make, for example, the trial and error process extremely long and complicated which in turn makes the attempt financially unsound. It is of course the ultimate goal of an encryption system to encode the to-be-transmitted data in such a manner that deciphering by unauthorized means is impossible even with an unlimited budget of time and computing power. Applicants have directed their attention to the solution of this problem which attention and effort has resulted in the to-be-described encoder/decoder apparatus.